Metal Cleaning Made Easy A fluidized bed system is a cost-effective option for degreasing processes. By M. Barletta, S. Guarino, and V1. Tagliaferri, University of Rome "Tot Vergata," Department of Mechanical Engineering T raditional degreasing processes employ chlori. hated solvents in a liquid or vapor state in order to remove oils and oil-borne soils from previously processed parts, such as chips, metal fines, and fluxes. Nevertheless, increased sensitivity to the environmental impacts of cleaning agents has led to alternative cleaning processes. A novel and unpublished eco-efficient degreasing technique has been analyzed in this study, namely, surface cleaning by means of a fluidized bed of hard particles. A spherical-shaped glass powder with variable mesh sizes in the range of 100 to 800 microns was fluidized. The impact of fluidized particles on the metal sub- strate caused accurate cleaning of the surface of the workpiece without involving the use of any solvents and without damaging the surface of the part to be degreased. Attention was paid on the correlation between process parameters and the effectiveness of the cleaning operation. By experimentation, the trend of the removal rate over time was successfully plotted for several operative conditions. INTRODUCTION Cleaning processes remove soils and contaminants from the surface of ferrous and nonferrous materials with varying levels of efficiency.1 They represent one of the most important stages of modern transforma- tion processes in industries fabricating or assem- bling metal parts, such as in the manufacture of air- craft, appliance, automobiles, electronics, and railroad equipment. 1 Scientific literature reports many solutions (mechanical, chemical, thermal) TM, which present remarkable operative advantages. However, most of these solutions are highly inefficient if many thou- sands of parts have to be cleaned simultaneously. In this regard, laser and plasma cleaning5-6, even if a high quality treated surface is obtained from them, are unsuitable for high volumes of production because of the large operative time. The cleaning techniques suitable for high volumes of production are ultrasound cleaning and vapor degreasing. 2-4 Nevertheless, the most pressing prob- lem of these technologies lies in their use of solvents that have a severe impact on the environment. In fact, the need to dismiss the exhaust solvents after use is the causes of a growing problem related to the more severe EC directives for this sector. Due to the growing pressure from market compe- tition, there is a demand for alternative techniques. These should guarantee low operative costs, a dry part after the treatment, high volume of simultane- ously treated parts, high levels of operational effi- ciency, reliability and reproducibility, a high degree of compatibility with different materials, and safe operative conditions. In this context, a totally novel experimental system, based upon fluidization tech- nology7.s, was developed. The core of this system consists of a container, namely, the fluidization column, which is about half- filled with abrasive media, namely, the powders. 7 The powders, taken in a fluid-like state by feeding enough air in the fluidization column, are driven toward the soiled metal substrate, previously dipped in the column, causing the particles to impact on it and thereby removing the soils. This, in turn, results in accurate cleaning of the work-piece without the use of any solvents and without damaging the sur- face to be degreased. The system capability and cleaning efficiencywere carefully checked out by varying the operative con- ditions, that is, the air flow, abrasive size and treat- ment time. Experimental tests showed that a good surface cleaning and an accurate process control, by simply changing operative parameters, are achiev- able. In addition, a simultaneous low cost treatment of many products in short time, preserving the glob- al process efficiency, is also attainable. MATERIAL AND METHODS The Fluidized Bed System The experimental system was composed of a vertical unit, a homogenization section and an inserted air flux distributor, made of sintered bronze (Figure 1). The pressure drop, temperature and humidity along the bed were measured by using a set of probes December 2004 23